1. Field of the Invention
Embodiments of the invention relate to light emitting diode (LED) lighting apparatuses driven by AC power, and more particularly, to AC LED lighting apparatuses that may increase luminous flux with optimal efficiency through optimal arrangement of a plurality of light emitting blocks on a circuit board and a plurality of LEDs and drive ICs included in each is of the light emitting blocks to be sequentially driven, and/or through efficient series-parallel connection between a limited number of LEDs.
2. Discussion of the Background
Generally, a light emitting diode package includes a light emitting diode chip, a lead frame, and a package body. The lead frame includes a plurality of terminals having different polarities. The package body serves to support the lead frame. The terminals extend from the interior of the package body to the outside of the package body. The light emitting diode chip is electrically connected to the terminals inside the package body. The package body is generally formed of a plastic resin or ceramic material. The package body of the plastic material may have a cavity, which receives the light emitting diode chip while optically exposing the light emitting diode chip therethrough, or may be at least partially transparent to allow light generated in the light emitting diode chip to be emitted to the outside therethrough.
A light emitting diode (LED) is a semiconductor device formed of semiconductor materials, such as gallium (Ga), phosphorous (P), arsenic (As), indium (In), nitrogen (N), aluminum (Al), and the like. LEDs have characteristics of a diode and emit red, green or blue light upon application of electric current thereto. LEDs are broadly used in the art, due to various advantages of longer lifespan, faster response rate (time between application of current and light emission) and lower power consumption than electric bulbs.
Generally, a light emitting diode can be driven only by DC power due to inherent characteristics of diode. As a result, a light emitting device employing such a conventional light emitting diode is limited in applicability and requires a separate circuit such as an SMPS when used in domestic settings employing AC power, thereby complicated circuit design of a lighting apparatus while increasing manufacturing costs.
To solve such problems, studies have focused on development of a light emitting device capable of being driven by AC power by connecting a plurality of light emitting cells to each other in series-parallel.
FIG. 1 is a block diagram of an AC LED lighting apparatus in the related art, and FIG. 2 is a waveform diagram of rectified voltage and LED driving current of the AC LED lighting apparatus of FIG. 1.
As shown in FIG. 1, the AC LED lighting apparatus in the related art includes a rectifier 10 which receives AC voltage from an AC power source VAC and outputs rectified voltage Vrec through full-wave rectification, first to fourth light emitting groups 20, 22, 24, 26 which are sequentially driven by the rectified voltage Vrec, a drive controller 40 which controls sequential driving of the first to fourth light emitting groups 20, 22, 24, 26 according to a voltage level of the rectified voltage Vrec, and first to fourth light emitting group drivers SW1, SW2, SW3, SW4, which have a switching function and a constant current controlling function.
Referring to FIG. 2, in operation of the AC LED lighting apparatus, the drive controller 40 determines a voltage level of rectified voltage Vrec applied by the rectifier 10, and sequentially drives the first to fourth light emitting groups 20, 22, 24, 26 according to the determined voltage level of the rectified voltage Vrec.
Thus, in zones in which the voltage level of the rectified voltage Vrec is greater than or equal to a first threshold voltage VTH1 and is less than a second threshold voltage VTH2 (t1˜t2 and t7·t8 in a single cycle of the rectified voltage), the drive controller 40 maintains a first switch SW1 in an on state and maintains a second switch SW2, a third switch SW3 and a fourth switch SW4 in an off state to allow only the first light emitting group 20 to be driven.
In addition, in zones in which the voltage level of the rectified voltage Vrec is is greater than or equal to the second threshold voltage VTH2 and is less than a third threshold voltage VTH3 (t2˜t3 and t6˜t7 in a single cycle of the rectified voltage), the drive controller 40 maintains the second switch SW2 in an on state and maintains the first switch SW1, the third switch SW3 and the fourth switch SW4 in an off state to allow only the first light emitting group 20 and the second light emitting group 22 to be driven.
Further, in zones in which the voltage level of the rectified voltage Vrec is greater than or equal to the third threshold voltage VTH3 and is less than a fourth threshold voltage VTH4 (t3˜t4 and t5˜t6 in a single cycle of the rectified voltage), the drive controller 40 maintains the third switch SW3 in an on state and maintains the first switch SW1, the second switch SW2 and the fourth switch SW4 in an off state to allow the first light emitting group 20, the second light emitting group and the third light emitting group 24 to be driven.
Further, in zones in which the voltage level of the rectified voltage Vrec is greater than or equal to the fourth threshold voltage VTH4 (t4˜t5 in a single cycle of the rectified voltage), the drive controller 40 maintains the fourth switch SW4 in an on state and maintains the first switch SW1, the second switch SW2 and the third switch SW3 in an off state to allow all of the first to fourth light emitting groups 20, 22, 24, 26 to be driven.
In such a conventional AC LED lighting apparatus as shown in FIG. 1, although luminous flux can be regulated by adjusting the number of LEDs constituting each of the light emitting groups in the LED lighting apparatus, there can be a problem of inefficiency in adjustment of the number of LEDs constituting each of the light emitting groups. In other words, although the number of LEDs in each of the light emitting groups can be increased to increase luminous flux of the LED lighting apparatus, the number of LEDs to be added to the LED lighting apparatus may be limited due to physical limitations (such as a maximum value of the is rectified voltage Vrec, a forward voltage level of the light emitting groups, the number of LEDs to be included in the LED lighting apparatus, manufacturing costs, and the like). However, conventional techniques do not provide arrangement of LEDs (series-parallel connection between LEDs) capable of achieving effective improvement of luminous flux of the LED lighting apparatus using a limited number of LEDs.
On the other hand, the conventional AC LED lighting apparatus as described above allows only a limited number of LEDs to be driven according to the standard of an AC power source connected thereto. Accordingly, in the case of illuminating a wider area, the aforementioned conventional AC LED lighting apparatus employing a sequential driving manner cannot be used. Thus, in manufacture of a large LED lighting apparatus, a separate power source circuit such as an SMPS is used. Use of the separate power source circuit such as the SMPS in manufacture of such a large LED lighting apparatus requires complex circuitry and increases manufacturing costs. Thus, there is an increasing need for a large LED lighting apparatus using a sequential drive type AC direct LED drive IC. However, when the large LED lighting apparatus employs a single sequential drive type AC direct LED drive IC, it is difficult for the large LED lighting apparatus to achieve uniform illumination due to individual driving of the plural light emitting blocks including a plurality of light emitting groups sequentially driven according to a voltage level of rectified voltage applied thereto. Therefore, there is a need for improved arrangement of LEDs on a circuit board in order to solve such a problem. However, in manufacture of large LED lighting apparatuses using a sequential drive type AC direct LED drive IC to provide uniform illumination, techniques in the related art do not provide a clear solution for improved and structural LED arrangement.